ИСТИНА

The express assessment of the planned hydrotechnical construction in the territory of Mongolia influence on change of volume and the mode of the Selenga River flow is executed. The expected influence of four planned water-engineering systems are considered: three of them on tributaries of Selenga and one on the main course. Predesigns showed that as a result of increase in losses of water at evaporation in river systems at formation of reservoirs (without losses of drain on their filling), the drain of the regulated rivers will be reduced in the sum in a year on 0,11 km3 that makes no more than 0,5% of the size of an average annual drain of the Selenga River near the mouth according to the station Mostovoy. Taking into account the planned transfer of a drain from the basin of Orkhon River the total loss will make 0,7-0,9% of a drain of the Selenga River in the mouth. At the sizes stated above, decrease in water level in the Lake Baikal will make at most 1 cm/year. The multivariant assessment of drain change of the Selenga River and its inflows at construction of reservoirs is executed. Operation of water-engineering systems will reduce intra annual fluctuations of a drain of the river by 1,12-1,15 times, reducing the maximum average monthly drain from 5-6% to 14-15%, increasing minimum winter by size from 57-63% to 73-75%. The short review of of Baikal fish fauna researches showed that the greatest loss to reproduction of valuable breeds of fishes will be caused by construction of the water-engineering system (Shuren hydroelectric power station) on the main course. The reservoir on the Orkhon river can be a source for flood of the region of the developing industry and can be the potentially perspective to dilute pollution arriving with right-bank inflows in the shallow water period. It is necessary to study the possibility of increase of its useful volume for partial compensation of power losses at refusal of a construction Shuren of hydroelectric power station.